Hemifield-Specific Rotational Biases During the Observation Of

S S symmetry

Article Hemiﬁeld-Speciﬁc Rotational Biases during the Observation of Ambiguous Human Silhouettes

Chiara Lucafò *,† , Daniele Marzoli *,†, Caterina Padulo , Stefano Troiano, Lucia Pelosi Zazzerini, Gianluca Malatesta , Ilaria Amodeo and Luca Tommasi

Department of Psychological Sciences, Health and Territory, University of Chieti, Via dei Vestini 29, I-66013 Chieti, Italy; [email protected] (C.P.); [email protected] (S.T.); [email protected] (L.P.Z.); [email protected] (G.M.); [email protected] (I.A.); [email protected] (L.T.) * Correspondence: [email protected] (C.L.); [email protected] (D.M.) † These authors equally contributed to this work.

Abstract: Both static and dynamic ambiguous stimuli representing human bodies that perform unimanual or unipedal movements are usually interpreted as right-limbed rather than left-limbed, suggesting that human observers attend to the right side of others more than the left one. Moreover, such a bias is stronger when static human silhouettes are presented in the RVF (right visual field) than in the LVF (left visual field), which might represent a particular instance of embodiment. On the other hand, hemispheric-specific rotational biases, combined with the well-known bias to perceive forward-facing figures, could represent a confounding factor when accounting for such findings. Therefore, we investigated whether the lateralized presentation of an ambiguous rotating human body would affect its perceived handedness/footedness (implying a role of motor representations), Citation: Lucafò, C.; Marzoli, D.; its perceived spinning direction (implying a role of visual representations), or both. To this aim, we Padulo, C.; Troiano, S.; required participants to indicate the perceived spinning direction (which also unveils the perceived Pelosi Zazzerini, L.; Malatesta, G.; handedness/footedness) of ambiguous stimuli depicting humans with an arm or a leg outstretched. Amodeo, I.; Tommasi, L. Hemifield-Specific Rotational Biases Results indicated that the lateralized presentation of the stimuli affected both their perceived limb during the Observation of laterality (a larger number of figures being interpreted as right-limbed in the RVF than in the LVF) Ambiguous Human Silhouettes. and their perceived spinning direction (a larger number of figures being interpreted as spinning Symmetry 2021, 13, 1349. https:// clockwise in the LVF than in the RVF). However, the hemifield of presentation showed a larger effect doi.org/10.3390/sym13081349 size on the perceived spinning direction than on the perceived limb laterality. Therefore, as we already proposed, the implicit representation of others’ handedness seems to be affected more by Academic Editor: Vilfredo De Pascalis visual than by motor processes during the perception of ambiguous human silhouettes.

Received: 20 May 2021 Keywords: human body; ambiguous figures; handedness/footedness; divided visual field paradigm; Accepted: 26 June 2021 lateralized embodiment; optic flow Published: 26 July 2021

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in 1. Introduction published maps and institutional affil- iations. In recent studies [1–4], we found that when right- and left-handed subjects were required to indicate the orientation of ambiguous (in terms of front or back view) figures representing human silhouettes in the act of performing one-handed manual actions, both groups reported perceiving the figures more frequently as oriented consistently with a right-handed movement than with a left-handed movement. Similar findings were re- Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. ported for dynamic stimuli representing ambiguous human bodies represented in the act This article is an open access article of performing unimanual and unipedal movements [3,5,6]. These results indicate an atten- distributed under the terms and tional/perceptual bias toward the right side of the human body and are also consistent with conditions of the Creative Commons findings from research investigating the perception of sport actions, according to which the Attribution (CC BY) license (https:// outcomes of right-limbed movements can be anticipated better than the outcomes of left- creativecommons.org/licenses/by/ limbed movements [7–13]. Noteworthy, this difference is present regardless of observers’ 4.0/). handedness [7,11], which is in contrast with the proposal that the correspondence between

Symmetry 2021, 13, 1349. https://doi.org/10.3390/sym13081349 https://www.mdpi.com/journal/symmetry Symmetry 2021, 13, 1349 2 of 19

observed movements and stored representations could foster action recognition (see [14] for a review). According to Hagemann [7] and Loffing, Schorer, et al. [9] (see also [8,10,11,13]), the ability to discriminate left-handed actions would be lower than that to discriminate right-handed actions (the same would hold true for foot movements), a difference likely due to a perceptual frequency effect (see also [15]): given that both right- and left-handers usually play against right- rather than left-handed opponents, the discrimination of right- handed actions would be easier for both groups in several interactive sports, in agreement with theories that emphasize the crucial role of visual experience in action perception (e.g., [16]). From an evolutionary point of view, an attentional and perceptual bias in favor of right-handed movements might be adaptive in social life because most everyday social interactions occur with right- rather than left-handed individuals (see also [17] for a more detailed discussion). Specifically, such a bias would represent a perceptual preference to attend to the body region most likely including others’ right hand. Given that, compared with the left hand, the right hand is more used in both communicative and aggressive behaviors, the bias toward the right side of human bodies would increase the efficiency in monitoring such behaviors. Further findings in line with a bias toward the right limbs of human bodies are provided by studies employing biological motion represented through point-light animations [18]. For example, Thornton et al. [19] (see also [20]) found that a point-light walker exhibiting equal motion clues to either side, and hence ambiguous in terms of heading direction, was interpreted more often as right-facing than as left-facing. It should be noticed that, when a right-facing individual is observed, the right limbs are in the foreground, and thus such results support the presence of an attentional and perceptual bias in favor of the right side of others. The preference for perceiving right-limbed actions did not correlate with the degree of participants’ handedness in previous studies with ambiguous human body stimuli [1–5,19,20], and thus it is plausible that such tasks involve relatively more visual than motor processes. Nonetheless, there is also some evidence for a role of motor representations, at least under certain conditions. Indeed, in a series of psychophysical experiments, de Lussanet et al. [21] clearly showed that rightward-facing point-light walkers were better identified compared with leftward-facing ones in the RVF (right visual field), whereas leftward-facing walkers were better identified compared with rightward-facing ones in the LVF (left visual field). To explain this lateralized facing effect, the authors proposed that the lateralized embodiment of an observed point-light walker is facilitated when the side of the visual cortex that processes the stimulus corresponds with the side of the sensory-motor cortices that process the hemibody seen in the foreground (for consistent findings with body part stimuli, see [22,23]). Moreover, we found that static human silhouettes with ambiguous handedness were interpreted more frequently as right-handed in the RVF than in the LVF [2,4]. Therefore, it is plausible that the hemifield of presentation promotes a laterally biased perception of ambiguous human bodies on the basis of the motor representations stored in the more stimulated (i.e., contralateral) hemisphere. However, there is some evidence suggesting that the hemifield of presentation might also affect the perceived spinning direction of ambiguous stimuli for other, non-motoric, reasons. In particular, as already proposed by [24], the usual experience of optic flow (i.e., the motion patterns of objects in the visual field of the observer; [25,26]) could induce hemispheric-specific rotational biases when one observes rotating objects with an ambiguous spinning direction. Indeed, the experience of optic flow (which occurs during walking, running, driving, and other activities implying a forward motion) is represented by the constant movement of objects “toward” the observer, but is also analogous to the perception of the motion vectors on the visible surface of a cylinder rotating CW (clockwise) in the LVF, and of those on the visible surface of a cylinder rotating CCW (counterclockwise) in the RVF. Specifically, Alipour and Kazemi [24] found a significantly shorter duration of the CCW perception when a stimulus (the spinning dancer designed by Japanese web artist Nobuyuki Kaya- hara; http://www.procreo.jp/labo/labo13.html, accessed on 28 June 2021) was presented in the LVF rather than in the RVF. Moreover, Burton et al. [27] examined reaction times Symmetry 2021, 13, 1349 3 of 19

for CW and CCW mental rotations in the two hemifields, showing that CCW and CW rotations were more efficiently performed in the RVF and LVF, respectively. We point out that a hemifield-specific rotational bias could also account for previous findings with static human silhouettes [2–4]. Indeed, a perceptual bias for forward-facing motion exists [28,29] (see also [30]) that can also induce observers to interpret ambiguous figures consistently with a forward rather than backward motion [31–33] (see also [34]) and ambiguous human bodies as front-facing rather than back-facing [1–4,35,36] (for further instances of perceptual and attentional advantages for approaching rather than receding stimuli, see [37–41]). Therefore, the combination of the bias to perceive forward-facing figures (which would be consistent with an inward rather than outward rotation) and the aforementioned hemifield- specific rotational bias could increase the proportion of left-sided silhouettes (i.e., those in which the action is depicted—from the observer’s point of view—on the figure’s left side) and right-sided silhouettes (i.e., those in which the action is depicted on the figure’s right side) interpreted as “potentially rotating” inward and CCW (and thus right-handed) in the RVF and as “potentially rotating” inward and CW (and thus left-handed) in the LVF. The same hemifield-specific rotational bias could account for de Lussanet et al.’s [21] findings: when a forward-facing stimulus located in one hemifield approaches (or is approached by) the observer, it appears to rotate until heading right (through a CCW rotation) or left (through a CW rotation) in the RVF and LVF, respectively. The same should apply to ambiguous stimuli (see [42]) because of the aforementioned perceptual bias for forward-facing motion. Interestingly, the hemifield-specific rotational bias might also account for certain links observed between perceptual and motor asymmetries (e.g., [43]). In summary, it has yet to be determined which specific factor is responsible for the tendency to interpret a larger number of ambiguous human bodies as right-handed in the RVF rather than in the LVF. Thus, the present study investigated whether the lateralized presentation of an ambiguous rotating human body affects its perceived handedness/footedness (in which case, mainly motor representations would be involved) or its perceived spinning direction (in which case, mainly visual representations would be involved), or both. To this aim, we used rotating stimuli depicting humans performing unimanual or unipedal movements.

2. Materials and Methods In agreement with the recommendations by Simmons, Nelson, and Simonsohn [44], we report how we deﬁned our sample sizes, as well as all manipulations, data exclusions, and measures in the study.

2.1. Participants One hundred and twenty-eight subjects (64 females and 64 males; age: 18–39 years) participated in the study. Speciﬁcally, we scheduled the enrollment of eight male subjects and eight female subjects for each different combination of outstretched limb and response arrow spinning direction (CW or CCW), position (above or below), and color (red or green; see Procedure section). All subjects had normal or corrected-to-normal vision.

2.2. Stimuli We used two sets of 128 animations obtained from an animation originally created with the software Poser Pro 2012 (Smith Micro Software Inc., Pittsburgh, PA, USA), which represented the silhouette of a human male rotating around his vertical axis while maintain- ing a static posture (in the ﬁrst set of animations, the silhouette was depicted as standing on both legs with one arm outstretched and the other arm close to the body; in the second set of animations, the silhouette was depicted as standing on one leg with the other leg outstretched and both arms close to the body; Figure1). Given that the silhouette is portrayed in black on a blank background and that no obvious depth clue is available, the animations turn out to be ambiguous and can be interpreted either as rotating CW (a percept consistent with an outstretched left arm or right leg in the original animations) or as rotating CCW (a percept consistent with an outstretched right arm or left leg in the Symmetry 2021, 13, x FOR PEER REVIEW 4 of 19

the second set of animations, the silhouette was depicted as standing on one leg with the other leg outstretched and both arms close to the body; Figure 1). Given that the silhouette is portrayed in black on a blank background and that no obvious depth clue is available, the animations turn out to be ambiguous and can be interpreted either as rotating CW (a percept consistent with an outstretched left arm or right leg in the original animations) or as rotating CCW (a percept consistent with an outstretched right arm or left leg in the original animations). Then, we decomposed each original animation into its 32 constituent frames and created 64 different versions, each of which depicted a com- Symmetry 2021, 13, 1349 4 of 19 plete rotation of the silhouette, by reorganizing the 32 frames on the basis of starting frame and order (i.e., from the 1st to the 32nd and vice versa, from the 2nd to the 1st and vice versa,original and so animations). on). Such Then, an order we decomposed manipulation each originalpermitted animation to offset into any its 32association constituent between framesspinning and direction created 64 and different outstretched versions, eacharm/leg of which by including depicted a completetwo rotation rotation condi- of the tions (e.g.,silhouette, see [3,5,6] by). reorganizing In the first condition, the 32 frames the on silhouette the basis of turns starting inward frame (i.e., and order“palmward” (i.e., from with referencethe 1st to to the the 32nd hand and movement vice versa, from and the “en 2nd dedans” to the 1st—a and term vice describing versa, and so a on). spin Such in which thean ballet order manipulationdancer turns permitted toward the to offset supporting any association leg—with between reference spinning to the direction foot and outstretched arm/leg by including two rotation conditions (e.g., see [3,5,6]). In the movement). In the second condition, the silhouette turns outward (i.e., “backward” with first condition, the silhouette turns inward (i.e., “palmward” with reference to the hand referencemovement to the hand and movement “en dedans”—a and “en term dehors” describing—a term a spin describing in which the a spin ballet in dancer which turns the ballet dancertoward turns the away supporting from leg—with the supporting reference leg to— thewith foot reference movement). to Inthe the foot second movement). condition, In the “inward”the silhouette order turns, the outwardCW rotation (i.e., “backward” is congruent with with reference an outstretched to the hand movementleft arm/leg, and whereas “enin the dehors”—a “outward” term order describing, the CW a spinrotation in which is congruent the ballet with dancer an turnsoutstretched away from right the arm/leg, andsupporting vice versa leg—with for the reference CCW rotation. to the foot We movement). set the Poser In theparameters “inward” (e.g., order, camera the CW distance rotationand camera is congruent elevation) with so an as outstretched to remove left—to arm/leg, the extent whereas possible in the— “outward”any potential order, perspectivethe clu CWe rotation(e.g., relative is congruent size and with relative an outstretched height). rightHowever, arm/leg, we andmirrored vice versa horizon- for the CCW rotation. We set the Poser parameters (e.g., camera distance and camera elevation) so tally each frame so as to create a further set of 64 animations, which permitted to offset as to remove—to the extent possible—any potential perspective clue (e.g., relative size and the effectsrelative of any height). remaining However, unwanted we mirrored asymmetry horizontally or depth each cue frame that so might as to create have abiased further the perceptionset of 64of animations,the outstretched which limb permitted (obviously, to offset this the manipulation effects of any remaining did not affect unwanted the associationasymmetry between orspinning depth cue direction that might and have outstretched biased the perception arm/leg in of either the outstretched order condi- limb tion/type(obviously, of this rotation; manipulation see did notexamples affect the association of possible between spinning percepts direction at https://osf.io/xrn4y/?view_onland outstretched arm/legy=cd558b56e03b4ff9a9c54eb16d464040, in either order condition/type of rotation; accessed see examples on 28 ofJune pos- 2021). Thesible 128 percepts animations at https://osf.io/xrn4y/?view_only=cd558b56e03b4ff9a9c54eb16d464040 of each set of stimuli represented each possible combination of , mirroring,accessed type of on rotation 28 June (inward 2021). The or 128outward) animations, and ofstarting each set frame. of stimuli Furthermore, represented these each possible combination of mirroring, type of rotation (inward or outward), and starting 128 final animations were presented once on the right side of the screen and once on the frame. Furthermore, these 128 final animations were presented once on the right side left side of the screenscreen and (after once the on onset the left of sidea fixation of the screencross remaining (after the onset in the of acenter fixation of crossthe screen untilremaining stimulus in theoffset) center so ofas the to screenobtain until 256 stimulustrials. At offset) a 57 cm so as viewing to obtain distance, 256 trials. the At frames composinga 57 cm viewing each distance, animation the measuredframes composing about each10.3° animation vertically measured and, on about average, 10.3◦ about 3.7°vertically horizontally. and, on Half average, of the about participants 3.7◦ horizontally. observed Half the of first the participantsset of animations observed (sil- the houette withfirst setone of arm animations outstretched) (silhouette and with the oneother arm half outstretched) observed the and second the other set half of observedanima- tions (silhouettethe second with set one of animations leg outstretched). (silhouette with one leg outstretched).

(a)

Figure 1. Cont.

Symmetry 2021, 13, x FOR PEER REVIEW 5 of 19 Symmetry 2021, 13, 1349 5 of 19

(b)

(c)

(d)

Figure 1. ExamplesFigure 1. Examplesof stimuli ofwith stimuli an arm with outstretched an arm outstretched (a,b) and (a with,b) and a leg with outstretched a leg outstretched (c,d) on (c ,d) on the the right (a,c) and on the left (b,d) of the fixation cross. right (a,c) and on the left (b,d) of the ﬁxation cross.

2.3. Procedure2.3. Procedure The experiThement experiment was performed was performed with SuperLab with SuperLab 4.0 (Cedrus 4.0 Corporation, (Cedrus Corporation, San Pedro, San Pedro, CA, USA)CA, on USA) a Windows on a Windows (Microsoft (Microsoft Corporation, Corporation, Redmond, Redmond, WA, WA, USA) USA) notebook notebook equipped equippedwith with an an Intel Intel (Intel (Intel Corporation, Corporation, Santa Santa Clara, Clara, CA, USA) CA, processor USA) processor and a 15.4-inch and a monitor. 15.4-inch Participantsmonitor. Participants were tested were in atested quiet in room, a quiet seated room, at aseated 57 cm at viewing a 57 cm distanceviewing from the distance from the computer screen, and they were invited to put their hands palms down

SymmetrySymmetry2021 2021,,13 13,, 1349 x FOR PEER REVIEW 66 of 1919

computer screen, and they were invited to put their hands palms down on the table and noton the to crosstable anyand bodynot to part cross (i.e., any legs, body arms, part or (i.e., fingers) legs, throughoutarms, or fingers) the experiment. throughout The the experimentexperiment. consistedThe experiment of 256 trialsconsisted (128 of right 256 trials trials and (128 128 right left trials trials) and in 128 each left of whichtrials) in a blackeach of fixation which cross a black presented fixation in cross the center presented of a blank in the screen center was of followeda blank screen after 500 was ms fol- by onelowed of theafter stimuli 500 ms described by one of previously the stimuli presented describe laterallyd previously (12.4 ◦presentedfrom the fixationlaterally point)(12.4° forfrom 2300 the ms fixation and then point) by for a couple 2300 ms of and colored then arrows—one by a couple of located colored slightly arrows above—one and located the otherslightly located above slightly and the below other thelocated center slightly of the below screen—depicting the center of thethe twoscreen possible—depicting spinning the directionstwo possible of the spinning silhouette directions (Figure 2of). t Participantshe silhouette were (Figure asked 2). to Participants gaze at the fixationwere asked point to andgaze to at report the fixation the perceived point and spinning to report direction the perceived of the silhouette spinning by direction pronouncing of the thesilhouette words “ROSSO”by pronouncing (the Italian the word words for “RED”) “ROSSO” and (the “VERDE” Italian (“GREEN”) word for according “RED”) to and their “VERDE” percept. After(“GREEN”) the participant’s according response to their percept. was recorded After bythe the participant’s experimenter, response who was was seated recorded behind by thethe participantexperimenter, and who pressed was theseated key behind “R” or the “V” participant on a keyboard and connectedpressed the to key the “R” notebook, or “V” theon a next keyboard trial started. connected to the notebook, the next trial started.

FigureFigure 2.2. SchematicSchematic representationrepresentation ofof thethe timetime coursecourse ofof aa trial.trial.

TheThe firstfirst frameframe ofof eacheach animationanimation lastedlasted 750750 ms,ms, andand thethe remainingremaining 3131 framesframes lastedlasted 5050 ms. ms. This This expedient expedient was was adopted adopted in order in order to reduce to reduce the possible the possible carry-over carry of-over responses of re- betweensponses between consecutive consecutive trials (e.g., trials see (e.g., [45], see where [45], perceptwhere percept carry-over carry was-over observed was observed even wheneven when a 30 sa break30 s break was introducedwas introduced after after the presentation the presentation of each of each ambiguous ambiguous spinning spin- dancer).ning dancer). Moreover, Moreover, we collected we collected subjects’ subjects’ responses responses by using by using two colored two colored arrows, arrows, each depictingeach depicting a possible a possible spinning spinning direction, direction, rather rather than usingthan using simple simple vocal vocal responses responses such assuch “ORARIO” as “ORARIO” and “ANTIORARIO” and “ANTIORARIO” (the Italian (the words Italian for words “CLOCKWISE” for “CLOCKWISE” and “COUN- and TERCLOCKWISE”,“COUNTERCLOCKWISE”, respectively), respect givenively), that given the latterthat the response latter modalityresponse turnsmodality out toturns be ratherout to troublesomebe rather troublesome for observers for observers (likely due (likely to the due difficulty to the difficulty in labeling in aslabeling CW or as CCW CW aor rotation CCW a aroundrotation anaround axis thatan axis is roughlythat is roughly parallel parallel to one’s to ownone’sbody own body axis). axis Before). Before the experiment,the experiment, participants participants were were familiarized familiarized with with the response the response modality modality by administering by adminis- themtering a them pretest a pretest in which in theywhich reported—by they reported means—by means of the twoof the response two response arrows arrows described de- above—the spinning direction of a black human silhouette that contained perspective cues scribed above—the spinning direction of a black human silhouette that contained per- (in particular, the relative size of the hands in distinct positions). Such a pretest permitted spective cues (in particular, the relative size of the hands in distinct positions). Such a the exclusion from the study of the few subjects who were not able to perform the task. pretest permitted the exclusion from the study of the few subjects who were not able to Each stimulus was shown twice, once to each hemifield, and the stimuli were presented in perform the task. Each stimulus was shown twice, once to each hemifield, and the stimuli a random sequence. were presented in a random sequence. The participant’s face was recorded throughout the experiment by means of the The participant’s face was recorded throughout the experiment by means of the computer-integrated webcam. This allowed the monitoring of her/his eye movements computer-integrated webcam. This allowed the monitoring of her/his eye movements in in order to discard trials in which she/he moved her/his gaze from the fixation point. order to discard trials in which she/he moved her/his gaze from the fixation point. Fi- Finally, the participant’s hand preference was assessed by means of the Italian version nally, the participant’s hand preference was assessed by means of the Italian version of of the Edinburgh Handedness Inventory [46]. The study was carried out following the the Edinburgh Handedness Inventory [46]. The study was carried out following the

Symmetry 2021, 13, 1349 7 of 19

guidelines of the Declaration of Helsinki, and it was authorized by the Institutional Review Board of Psychology of the Department of Psychological Sciences, Health, and Territory of the University of Chieti (protocol code 21003). A written informed consent was provided by each participant.

2.4. Data Analysis Twenty-five subjects (15 males and 10 females) were excluded from the analysis due to problems in video recording, and 2 subjects (both male) were excluded because they always gave the same response (RED or GREEN). The trials in which subjects moved their eyes from the fixation point were eliminated, and 7 other subjects (4 males and 3 females) were excluded because the proportion of displacements exceeded 15%. On the basis of their laterality score on the Italian version of the Edinburgh Handedness Inventory [46], the remaining 94 subjects were categorized as right-handers (87 subjects exhibiting a positive laterality score; range: 0.15/1.00; M = 0.65 ± 0.023 SEM) or left-handers (7 subjects exhibiting a negative laterality score; range: −0.81/−0.14; M = 0.52 ± 0.076 SEM). Two different analyses were carried out to test whether (1) the perceived limb laterality and (2) the perceived spinning direction of the figure were affected by the hemifield of presentation, the type of rotation, the outstretched limb, participants’ sex, and/or their interactions. Initially, we computed for each participant eight measures indicating the number of figures interpreted as right- and left-limbed and eight measures representing the number of figures interpreted as rotating CW and CCW in any combination of hemifield of presentation and type of rotation. Then, 2 female participants and 3 male participants were excluded as outliers because they scored at least 2 standard deviations above or below the average of their experimental group (arm or leg) in any of the aforementioned measures. Finally, we performed two repeated-measures analyses of variance (ANOVAs). In the first, we used participant’s sex (female or male) and the outstretched limb (arm or leg) as between-subjects factors, and the side of hemifield presentation (right or left) and perceived limb laterality (right or left) as within-subjects factors. In the second, we used participant’s sex (female or male) and the outstretched limb (arm or leg) as between-subjects factors, and the side of hemifield presentation (right or left) and perceived spinning direction (CW or CCW) as within-subjects factors. As evident in Table1, coding the percept according to limb laterality or spinning direction permutes the roles of main effects and interactions while leaving identical F- and p-values. When needed, we carried out post-hoc t-tests in order to determine the significant differences (within each set of post-hoc contrasts, p-values were adjusted according to the Bonferroni correction for multiple comparisons). Participants’ handedness was not included as an independent variable in the ANOVAs performed due to the low number of left-handers, so participants’ laterality score was correlated with the percentage of figures interpreted as right-limbed and the percentage of figures interpreted as rotating CW.

Table 1. Correspondences between the results of ANOVAs with percepts coded according to limb laterality and spinning 2 direction. Effect size (ηp ) and observed power (1 − β) for each signiﬁcant effect (computed for α = 0.05) are also reported.

Factors Statistics Perceived Limb Laterality Perceived Spinning Direction

F1,85 = 3.994 p = 0.049 Perceived limb laterality Type of rotation X Perceived spinning direction 2 ηp = 0.045 1 − β = 0.506

F1,85 = 5.376 Hemiﬁeld of presentation X Perceived Hemiﬁeld of presentation X The type of rotation X p = 0.023 2 limb laterality Perceived spinning direction ηp = 0.059 1 − β = 0.630 Symmetry 2021, 13, 1349 8 of 19

Table 1. Cont.

Factors Statistics Perceived Limb Laterality Perceived Spinning Direction

F1,85 = 7.763 Type of rotation X Participant’s sex X Perceived p = 0.007 Participant’s sex X Perceived limb laterality 2 spinning direction ηp = 0.084 1 − β = 0.787

F1,85 = 11.654 Hemiﬁeld of presentation X Type of rotation X Hemiﬁeld of presentation X Perceived p < 0.001 2 Perceived limb laterality spinning direction ηp = 0.121 1 − β = 0.921

F1,85 = 6.002 Type of rotation X Outstretched limb X Outstretched limb X Participant’s sex X Perceived p = 0.016 2 Participant’s sex X Perceived limb laterality spinning direction ηp = 0.066 1 − β = 0.678 F = 4.576 Hemiﬁeld of presentation X Type of rotation X 1,85 Hemiﬁeld of presentation X Outstretched limb X p = 0.035 Outstretched limb X Participant’s sex X Participant’s sex X Perceived spinning direction η 2 = 0.051 Perceived limb laterality p 1 − β = 0.562

3. Results The first ANOVA, which examined perceived limb laterality, showed: a significant main effect of perceived limb laterality (F1,85 = 3.994; p = 0.049); a significant interaction between the hemifield of presentation and perceived limb laterality (F1,85 = 5.376; p = 0.023); a significant interaction between participant’s sex and perceived limb laterality (F1,85 = 7.763; p = 0.007); a significant interaction between the hemifield of presentation, type of rotation, and perceived limb laterality (F1,85 = 11.654; p < 0.001); a significant interaction between the type of rotation, outstretched limb, participant’s sex, and perceived limb laterality (F1,85 = 6.002; p = 0.016); and a significant interaction between the hemifield of presentation, type of rotation, outstretched limb, participant’s sex, and perceived limb laterality (F1,85 = 4.576; p = 0.035). Participants’ laterality score did not correlate with the percentage of figures interpreted as right-limbed (n = 89; r = −0.037; p = 0.727). Participants perceived a larger number of right-limbed (M = 51.54%) rather than left- limbed figures (M = 48.46%). However, this difference held true in the RVF (right-limbed: M = 52.54%; left-limbed: M = 47.46%; t88 = 2.675, p = 0.018) but not in the LVF (right-limbed: M = 50.55%; left-limbed: M = 49.45%; t88 = 0.558, p = 1). Moreover, a larger number of figures were interpreted as right-limbed in the RVF than in the LVF (t88 = 2.227, p = 0.028; Figure3). Male participants perceived a larger number of right- (M = 54.01%) rather than left- limbed figures (M = 45.99%; t39 = 4.152; p < 0.001), whereas no difference was observed in female participants (right-limbed: M = 49.53%; left-limbed: M = 50.47%; t48 = −0.368; p = 1). Moreover, the number of figures interpreted as right-limbed was larger for male than for female participants (t87 = 2.695; p = 0.008; Figure4). In the LVF, participants perceived a larger number of right- (M = 58.08%) rather than left-limbed figures (M = 41.92%; t88 = 3.164, p = 0.009) in the outward-rotation condition and a larger number of left- (M = 56.99%) rather than right-limbed figures (M = 43.01%; t88 = 2.613, p = 0.042) in the inward-rotation condition. In the RVF, no difference was observed in both the outward- (right-limbed: M = 49.07%; left-limbed: M = 50.93%; t88 = −0.382, p = 1) and inward-rotation condition (right-limbed: M = 56.01%; left-limbed: M = 43.99%; t88 = 2.210, p = 0.119). Moreover, participants perceived a larger number of right-limbed figures in the RVF (M = 56.01%) than in the LVF (M = 43.01%; t88 = 3.490, p = 0.002) in the inward-rotation condition and a larger number of right-limbed figures in the LVF (M = 58.08%) than in the RVF (M = 49.07%; t88 = 2.678, p = 0.018) in the outward-rotation condition. Finally, in the LVF participants perceived a larger number of Symmetry 2021, 13, x FOR PEER REVIEW 8 of 19

ηp2 = 0.084 1 − β = 0.787 F1,85 = 11.654 Hemifield of presentation X Type of rotation X Hemifield of presentation X Perceived spin- p < 0.001 Perceived limb laterality ning direction ηp2 = 0.121 1 − β = 0.921 F1,85 = 6.002 Type of rotation X Outstretched limb X Partici- Outstretched limb X Participant’s sex X Per- p = 0.016 pant’s sex X Perceived limb laterality ceived spinning direction ηp2 = 0.066 1 − β = 0.678 F1,85 = 4.576 Hemifield of presentation X Type of rotation X Hemifield of presentation X Outstretched limb p = 0.035 Outstretched limb X Participant’s sex X Per- X Participant’s sex X Perceived spinning direc- ηp2 = 0.051 ceived limb laterality tion 1 − β = 0.562

3. Results The first ANOVA, which examined perceived limb laterality, showed: a significant main effect of perceived limb laterality (F1,85 = 3.994; p = 0.049); a significant interaction between the hemifield of presentation and perceived limb laterality (F1,85 = 5.376; p = 0.023); a significant interaction between participant’s sex and perceived limb laterality (F1,85 = 7.763; p = 0.007); a significant interaction between the hemifield of presentation, type of rotation, and perceived limb laterality (F1,85 = 11.654; p < 0.001); a significant interaction between the type of rotation, outstretched limb, participant’s sex, and perceived limb laterality (F1,85 = 6.002; p = 0.016); and a significant interaction between the hemifield of presentation, type of rotation, outstretched limb, participant’s sex, and perceived limb laterality (F1,85 = 4.576; p = 0.035). Participants’ laterality score did not correlate with the percentage of figures interpreted as right-limbed (n = 89; r = −0.037; p = 0.727). Symmetry 2021, 13, 1349 Participants perceived a larger number of right-limbed (M = 51.54%) rather9 of 19 than left-limbed figures (M = 48.46%). However, this difference held true in the RVF (right-limbed: M = 52.54%; left-limbed: M = 47.46%; t88 = 2.675, p = 0.018) but not in the right-limbed ﬁgures in the outward-rotation condition (M = 58.08%) than in the inward- 88 LVF (right-limbed:rotation condition M = 50.55%; (M = 43.01; left- tlimbed:88 = 3.108, Mp == 0.005),49.45%; whereas t = no0.558, difference p = 1). was Moreover, observed a larger numberin the of RVFfigures (outward were rotation:interpreted M = 49.07%;as right inward-limbed rotation: in the MRVF = 56.01%; than int88 the= − 1.443LVF, (t88 = 2.227, p = 0.028;p = 0.305; Figure Figure 3).5).

40 LEFT-LIMBED RIGHT-LIMBED LEFT-LIMBED RIGHT-LIMBED Symmetry 2021, 13, x FOR PEER REVIEW 9 of 19

LVF RVF

Male participants perceived a larger number of right- (M = 54.01%) rather than left-limbed figures (M = 45.99%; t39 = 4.152; p < 0.001), whereas no difference was observed Figure 3. PercentageFigurein female of 3. figuresparticipantsPercentage interpreted (right of figuresas- right-limbed: and interpreted M left-limbed = 49.53%; as according left right-limbed:- toand hemifield M left =- limbed50.47%; of presentation. accordingt48 = −0 Note:.368; to LVF,p = hemifield left of visual field;presentation. RVF,1). Moreover, right visual Note:the field. number LVF, left of figuresvisual field;interpreted RVF, rightas right visual-limbed field. was larger for male than for female participants (t87 = 2.695; p = 0.008; Figure 4).

40 LEFT-LIMBED RIGHT-LIMBED LEFT-LIMBED RIGHT-LIMBED FEMALE MALE

FigureFigure 4. 4.Percentage Percentage of of ﬁgures figures interpreted interpreted as right-as right and- and left-limbed left-limbed according according to participant’s to participant’s sex. sex.

In the LVF, participants perceived a larger number of right- (M = 58.08%) rather than left-limbed figures (M = 41.92%; t88 = 3.164, p = 0.009) in the outward-rotation condition and a larger number of left- (M = 56.99%) rather than right-limbed figures (M = 43.01%; t88 = 2.613, p = 0.042) in the inward-rotation condition. In the RVF, no difference was observed in both the outward- (right-limbed: M = 49.07%; left-limbed: M = 50.93%; t88 = −0.382, p = 1) and inward-rotation condition (right-limbed: M = 56.01%; left-limbed: M = 43.99%; t88 = 2.210, p = 0.119). Moreover, participants perceived a larger number of right-limbed figures in the RVF (M = 56.01%) than in the LVF (M = 43.01%; t88 = 3.490, p = 0.002) in the inward-rotation condition and a larger number of right-limbed figures in the LVF (M = 58.08%) than in the RVF (M = 49.07%; t88 = 2.678 p = 0.018) in the outward-rotation condition. Finally, in the LVF participants perceived a larger number of right-limbed figures in the outward-rotation condition (M = 58.08%) than in the inward-rotation condition (M = 43.01; t88 = 3.108, p = 0.005), whereas no difference was observed in the RVF (outward rotation: M = 49.07%; inward rotation: M = 56.01%; t88 = −1.443, p = 0.305; Figure 5).

Symmetry 2021, 13, x FOR PEER REVIEW 10 of 19 Symmetry 2021, 13, 1349 10 of 19

LEFT-LIMBED LEFT-LIMBED LEFT-LIMBED LEFT-LIMBED

RIGHT-LIMBED RIGHT-LIMBED RIGHT-LIMBED RIGHT-LIMBED INWARD OUTWARD INWARD OUTWARD LFV RVF

Figure 5. FigurePercentage 5. Percentage of figures interpretedof figures interpreted as right- and as left-limbed right- and according left-limbed to typeaccording of rotation to type and of hemifield rotation of presentation.and Note: hemifield LVF, left of visualpresentation. field; RVF, Note: right LVF, visual left field. visual field; RVF, right visual field.

In the inwardIn-rotation the inward-rotation condition of condition the leg-outstretched of the leg-outstretched version of version the experiment, of the experiment, male participantsmale perceived participants a perceivedlarger number a larger of number right- oflimbed right-limbed figures figures (M = (M 57.99%) = 57.99%) com- compared with female participants (M = 42.86%; t = 3.060; p = 0.015), and no significant difference pared with female participants (M = 42.86%; t46 = 3.060;46 p = 0.015), and no significant dif- was observed between male and female participants in the number of figures interpreted as ference was observed between male and female participants in the number of figures right-limbed in any of the remaining combinations of outstretched limb and type of rotation interpreted as right-limbed in any of the remaining combinations of outstretched limb (all p > 0.2; Supplementary Material Table S1). Moreover, female participants showed a and type of rotationstatistical (all trend p > to 0.2; perceive Supplementary a larger number Material of right-limbed Table S1 figures). Moreover, in the outward-rotation female participants showedcondition a statistical of the leg-outstretched trend to perceive version a larger of the number experiment of right (M-limbed = 58.47%) figures than in the in the outwardoutward-rotation-rotation condition condition of the of leg the- arm-outstretchedoutstretched version version of of the the experiment experiment (M(M = = 46.79%; 58.47%) than int47 the= 2.497; outwardp = 0.064),-rotation and no condition significant of difference the arm-outstretched was observed versionbetween ofthe the arm- and experiment (Mleg-outstretched = 46.79%; t47 = 2.497; versions p = of 0.064), the experiment and no significant in the number difference of figures was interpreted observed as right- between the armlimbed- and in leg any-outstretched of the remaining versions combinations of the experiment of participant’s in sexthe andnumber type ofof rotation fig- (all p ures interpreted> as 0.75 right; Supplementary-limbed in any Material of the Table remaining S2). Finally, combinations female participants of participant’s showed asex statistical trend to perceive a larger number of right-limbed figures in the outward-rotation condition and type of rotation (all p > 0.75; Supplementary Material Table S2). Finally, female par- (M = 58.47%) than in the inward-rotation condition (M = 42.86%; t27 = 2.616; p = 0.058) of ticipants showedthe a leg-outstretched statistical trend version to perceive of the experiment, a larger number and no significantof right-limbed difference figures was observedin the outward-rotationbetween condition the inward- (M and = outward-rotation58.47%) than in conditionsthe inward in- therotation number condition of figures (M interpreted = 42.86%; t27 = 2.616;as right-limbed p = 0.058) in of any the of theleg- remainingoutstretched combinations version of participant’sthe experiment, sex and and outstretched no significant differencelimb (all wasp = 1; observed Supplementary between Material the Table inward S3).- and outward-rotation conditions in the numberIn of the figures inward-rotation interpreted condition as right of-limbed the leg-outstretched in any of the version remaining of the com- experiment, binations of participant’smale participants sex and perceived outstretched a larger number limb (all of right-p = 1; (M Supplementary = 69.06%) rather Material than left-limbed Table S3). figures (M = 30.94%; t19 = 3.524; p = 0.036) in the RVF, and no significant difference was observed between the number of left- and right-limbed figures in any of the remaining com- In the inward-rotation condition of the leg-outstretched version of the experiment, binations of participant’s sex, outstretched limb, type of rotation, and hemifield of presen- male participantstation perceived (all p > 0.3; Supplementary a larger number Material of Tableright S4).- (M Moreover, = 69.06%) in the leg-outstretched rather than ver- left-limbed figuression of (M the =experiment, 30.94%; t19male = 3.524; participants p = 0.036) perceived in the aRVF, larger and number no significant of right-limbed dif- figures ference was observedin the RVF between (M = 69.06%) the number than in theof left LVF- and (M = right 46.92%;-limbed t19 = 3.299; figuresp = in 0.030) any inof the the inward- remaining combinationsrotation condition of participant’s and a larger sex, number outstretched of right-limbed limb, figures type of in therotation LVF (M, and = 59.62%) hemifield of presentationthan in the RVF (all (Mp > = 0.3; 40.53%; Supplementary t19 = 3.206; p =Material 0.037) in Table the outward-rotation S4). Moreover, condition, in the and leg-outstretchedno version significant of differencethe experim wasent, observed male participants between the perceived LVF and the a larger RVF in number the number of figures interpreted as right-limbed in any of the remaining combinations of participant’s of right-limbed figures in the RVF (M = 69.06%) than in the LVF (M = 46.92%; t19 = 3.299; p sex, outstretched limb, and type of rotation (all p > 0.08; Supplementary Material Table S5). = 0.030) in the inward-rotation condition and a larger number of right-limbed figures in the LVF (M = 59.62%) than in the RVF (M = 40.53%; t19 = 3.206; p = 0.037) in the outward-rotation condition, and no significant difference was observed between the LVF and the RVF in the number of figures interpreted as right-limbed in any of the remaining combinations of participant’s sex, outstretched limb, and type of rotation (all p > 0.08; Supplementary Material Table S5). Finally, in the inward-rotation condition of the

Symmetry 2021, 13, x FOR PEER REVIEW 11 of 19

Symmetry 2021, 13, 1349 11 of 19 leg-outstretched version of the experiment, male participants perceived a larger number of right-limbed figures (M = 69.06%) compared with female participants (M = 44.71%; t46 = 3.121; p = 0.025)Finally, in the inRVF, the inward-rotationand no significant condition difference of the was leg-outstretched observed between version of male the experiment,and female participantsmale participants in the number perceived of figures a larger number interpreted of right-limbed as right- figureslimbed (M in = any 69.06%) of the compared remaining combinationswith female of participants outstretched (M = limb, 44.71%; type t46 =of 3.121; rotationp = 0.025), and inhemifield the RVF, andof presen- no significant tation (all p > 0.08;difference Supplementary was observed Material between Table male S6). and female participants in the number of figures The secondinterpreted ANOVA, as which right-limbed examined in any perceived of the remaining spinning combinations direction, of showed outstretched: a sig- limb, type of rotation, and hemifield of presentation (all p > 0.08; Supplementary Material Table S6). nificant interaction between the hemifield of presentation and perceived spinning direc- The second ANOVA, which examined perceived spinning direction, showed: a signifi- tion (F1,85 = 11.654;cant interactionp < 0.001); between a significant the hemifield interaction of presentation between the and type perceived of rotation spinning and direction perceived spinning direction (F1,85 = 3.994; p = 0.049); a significant interaction between (F1,85 = 11.654; p < 0.001); a significant interaction between the type of rotation and perceived outstretched limb,spinning participant’s direction (F sex1,85, =and 3.994; perceivedp = 0.049); spinning a significant direction interaction (F1,85 between = 6.002; outstretched p = 0.016); a significantlimb, participant’sinteraction sex,between and perceived the type spinning of rotation, direction participant’s (F1,85 = 6.002; sexp, =and 0.016); per- a signif- ceived spinningicant direction interaction (F1,85 between = 7.763 the; p type= 0.007) of rotation,; a significant participant’s interaction sex, and between perceived the spinning hemifield of presentation,direction (F1,85 the= 7.763;type pof= rotation 0.007); a, significantand perceived interaction spinning between direction the hemifield (F1,85 = of pre- 5.376; p = 0.023)sentation,; and a significant the type of interaction rotation, and between perceived the spinning hemifield direction of presentation, (F1,85 = 5.376; out-p = 0.023); and a significant interaction between the hemifield of presentation, outstretched limb, stretched limb, participant’s sex, and perceived spinning direction (F1,85 = 4.576; p = 0.035). participant’s sex, and perceived spinning direction (F1,85 = 4.576; p = 0.035). Participants’ Participants’ lateralitylaterality score did did not not correlate correlate with with the percentagethe percentage of figures of figures interpreted interpreted as spinning CW as spinning CW(n (n = 89;= 89; r = r− =0.094; −0.094;p = p 0.382). = 0.382). Participants perceivedParticipants a perceived larger number a larger number of CW of- CW-(M =(M 57.53%) = 57.53%) rather rather than than CCW- CCW-spinningspinning figures figures(M = 42.47%; (M = 42.47%; t88 = t3.108,88 = 3.108, p = 0.005)p = 0.005) in the in the LVF, LVF, whereas whereas nono differencediffer- was ence was observedobserved in the in theRVF RVF (CW (CW-spinning:-spinning: M M = = 46.53%; 46.53%; CCW-spinning:CCW-spinning: M M = 53.47%;= 53.47%; t88 =t88− 1.443, = −1.443, p = 0.305).p = 0.305). Moreover, Moreover, a larger a larger number number of of figu figuresres werewere interpreted interpreted as spinningas spinning CW in the LVF than in the RVF (t = 3.204, p = 0.002; Figure6). CW in the LVF than in the RVF (t8888 = 3.204, p = 0.002; Figure 6).

40 CCW CW CCW CW LVF RVF

Figure 6. PercentageFigure 6. Percentage of figures interpreted of figures as interpreted spinning clockwise as spinning and counterclockwise clockwise and according counterclockwise to hemifield according of presentation. Note:to CW, hemifield clockwise; of CCW,presentation. counterclockwise; Note: CW, LVF, clockwise; left visual field;CCW, RVF, counterclockwise; right visual field. LVF, left visual field; RVF, right visual field. Participants showed a statistical trend to perceive a larger number of CW-spinning fig- Participantsures showed in the outward-rotation a statistical trend condition to perceive (M = 53.57%) a larger than number in the inward-rotation of CW-spinning condition figures in the outward(M = 50.49%;-rotation t88 = 1.803, conditionp = 0.075). (M = 53.57%) than in the inward-rotation con- In the leg-outstretched version of the experiment, female participants perceived a dition (M = 50.49%; t88 = 1.803, p = 0.075). larger number of CW-spinning figures (M = 57.80%) compared with male participants In the leg-outstretched version of the experiment, female participants perceived a (M = 46.04%; t46 = 2.528; p = 0.030), whereas no significant difference was observed between larger numbermale of CW and-spinning female participants figures (M = in 57.80%) the number compared of figures with interpreted male participants as spinning (M CW in = 46.04%; t46 = 2.528; p = 0.030), whereas no significant difference was observed between male and female participants in the number of figures interpreted as spinning CW in the arm-outstretched version of the experiment (female participants: M = 48.77%; male participants: M = 53.36%; t39 = 0.965; p = 0.681). Moreover, female participants showed a sta-

Symmetry 2021, 13, x SymmetryFOR PEER2021 REVIEW, 13, 1349 12 of 19 12 of 19

the arm-outstretched version of the experiment (female participants: M = 48.77%; male tistical trend toparticipants: perceive a Mlarger = 53.36%; number t39 = of 0.965, CW p(M= 0.681).= 57.80%) Moreover, rather femalethan CCW participants-spinning showed a figures (M = 42.20%;statistical t27 trend = 2.616; to perceive p = 0.058) a larger in numberthe leg- ofoutstretched CW (M = 57.80%) version rather of thanthe CCW-spinningexperi- ment, and no figuressignificant (M = 42.20%;difference t27 = was 2.616, observp = 0.058)ed between in the leg-outstretched the number version of figures of the inter- experiment, preted as spinningand no CW significant and CCW difference in any was of the observed remaining between combinations the number ofof figuresparticipant’s interpreted as spinning CW and CCW in any of the remaining combinations of participant’s sex and sex and outstretched limb (all p > 1; Supplementary Material Table S7). outstretched limb (all p > 1; Supplementary Material Table S7). Male participantsMale participantsperceived a perceived larger number a larger numberof CW- ofspinning CW-spinning figures figures in the in the out- outward- ward-rotation rotationcondition condition (M = 53.71%) (M = 53.71%)than in the than inward in the- inward-rotationrotation condition condition (M = 45.70%; (M = 45.70%; t39 = 4.152, p

40 CCW CW CCW CW CCW CW CCW CW INWARD OUTWARD INWARD OUTWARD FEMALE MALE

Figure 7. PercentageFigure 7. Percentage of ﬁgures interpreted of figures as interpreted spinning clockwise as spinning and counterclockwise clockwise and accordingcounterclockwise to type of according rotation and participant’sto sex.type Note: of rotation CW, clockwise; and participant’s CCW, counterclockwise. sex. Note: CW, clockwise; CCW, counterclockwise.

In the LVF, participantsIn the LVF, participantsperceived a perceived larger number a larger of number CW- (M of CW-= 56.99%) (M = 56.99%)rather than rather than CCW-spinningCCW-spinning figures (M = figures43.01%; (M t88 = = 43.01%; 2.613, p t88 = =0.042) 2.613, inp =the 0.042) inward in the-rotation inward-rotation condition, condition, and a larger numberand a larger of CW number-spinning of CW-spinning figures (M figures = 58.08%) (M = rather 58.08%) than rather CCW than-spinning CCW-spinning figures (M = 41.92%; t88 = 3.164, p = 0.009) in the outward-rotation condition. In the RVF, figures (M = 41.92%; t88 = 3.164, p = 0.009) in the outward-rotation condition. In the RVF, no difference was observed in both the inward- (CW-spinning: M = 43.99%; CCW-spinning: no difference was observed in both the inward- (CW-spinning: M = 43.99%; M = 56.01%; t88 = 2.210, p = 0.119) and the outward-rotation condition (CW-spinning: CCW-spinning: M = 56.01%; t88 = 2.210, p = 0.119) and the outward-rotation condition M = 49.07%; CCW-spinning: M = 50.93%; t88 = −0.382, p = 1). Moreover, participants (CW-spinning:perceived M = 49.07%; a larger CCW number-spinning: of CW-spinning M = 50.93%; figures t in88 the= − LVF0.382, (M p = = 56.99%) 1). Moreover, than in the RVF participants perceived(M = 43.99%; a larger t88 = 3.490,numberp = of 0.002) CW in-spinning the inward-rotation figures in condition,the LVF (M and = a56.99%) larger number than in the RVFof (M CW-spinning = 43.99%; figurest88 = 3.490, in the p LVF= 0.002) (M = in 58.08%) the inward than in-rotation the RVF condition, (M = 49.07%; and t88 a= 2.678, larger numberp of= 0.018CW)-spinning in the outward-rotation figures in the condition. LVF (M Finally,= 58.08%) in the than RVF, in participants the RVF (M perceived = a larger number of CW-spinning figures in the outward-rotation condition (M = 49.07%) than 49.07%; t88 = 2.678 p = 0.018) in the outward-rotation condition. Finally, in the RVF, par- in the inward-rotation condition (M = 43.99%; t = 2.675, p = 0.018), whereas no difference ticipants perceived a larger number of CW-spinning figures88 in the outward-rotation was observed in the LVF (outward-rotation: M = 58.08%; inward-rotation: M = 56.99%; condition (M = 49.07%) than in the inward-rotation condition (M = 43.99%; t88 = 2.675, p = t88 = 0.558, p > 1; Figure8). 0.018), whereas no difference was observed in the LVF (outward-rotation: M = 58.08%; inward-rotation: M = 56.99%; t88 = 0.558, p > 1; Figure 8).

Symmetry 2021, 13, x FOR PEER REVIEW 13 of 19 Symmetry 2021, 13, 1349 13 of 19

40 CCW CW CCW CW CCW CW CCW CW INWARD OUTWARD INWARD OUTWARD LVF RVF

Figure 8. PercentageFigure 8. Percentage of figures interpreted of figures as interpreted spinning clockwise as spinning and counterclockwise clockwise and accordingcounterclockwise to type of according rotation and hemifield ofto presentation.type of rotation Note: and CW, hemifield clockwise; CCW,of presentation. counterclockwise, Note: LVF,CW, left clockwise; visual field; CCW, RVF, rightcounterclockwise, visual field. LVF, left visual field; RVF, right visual field. Male participants perceived a larger number of CW-spinning figures in the LVF Male participants(M = 56.35% perceived) than in a the larger RFV (Mnumber = 35.73%; of CW t19 -=spinning 3.536, p = figures 0.009) inin the the leg-outstretched LVF (M = 56.35%) thanversion in the RFV of the (M experiment = 35.73%; but t19 = not 3.536; in the p = arm-outstretched 0.009) in the leg version-outstretched of the experimentver- sion of the experiment(CW-spinning but in the not LVF: in theM = 56.19%;arm-outstretched CW-spinning version in the RVF: of the M = experiment 50.54%; t19 = 0.911, p = 1), and female participants showed a statistical trend to perceive a larger number of (CW-spinning in the LVF: M = 56.19%; CW-spinning in the RVF: M = 50.54%; t19 = 0.911; p CW-spinning figures in the LVF (M = 57.52%) than in the RFV (M = 40.03%; t = 2.570, = 1), and female participants showed a statistical trend to perceive a larger number20 of p = 0.073) in the arm-outstretched version of the experiment but not in the leg-outstretched CW-spinning figuresversion ofin thethe experiment LVF (M = (CW-spinning57.52%) than in thethe LVF: RFV M (M = 59.35%;= 40.03%; CW-spinning t20 = 2.570; in p the= RVF: 0.073) in the armM =-outstretched 56.26%; t27 = 0.424,versionp =of 1). the Moreover, experiment in the but leg-outstretched not in the leg version-outstretched of the experi- version of thement, experiment female participants (CW-spinning perceived in the a larger LVF: number M = 59.35%; of CW-spinning CW-spinning figures in (M the = 56.26% ) RVF: M = 56.26%;compared t27 = 0.424; with malep = 1). participants Moreover, (M in = the 35.73%; leg-outstretched t46 = 2.858, p = version 0.026) in of the the RVF, ex- and no periment, femaledifference participants was observed perceived between a larger male number and female of participantsCW-spinning in the figures number (M of = figures interpreted as spinning CW in any of the remaining combinations of hemifield of presenta- 56.26%) compared with male participants (M = 35.73%; t46 = 2.858; p = 0.026) in the RVF, and no differencetion andwas outstretchedobserved between limb (all malep > 0.22; andSupplementary female participants Material in Table the S8number). Finally, of female participants showed a statistical trend to perceive a larger number of CW-spinning figures figures interpreted as spinning CW in any of the remaining combinations of hemifield of in the leg-outstretched version of the experiment (M = 56.26%) than in the arm-outstretched presentation and outstretched limb (all p > 0.22; Supplementary Material Table S8). Fi- version of the experiment (M = 40.03%; t47 = 2.460, p = 0.070) in the RVF, and no difference nally, female was participants observed between showed the a arm- statistical and leg-outstretched trend to perceive version aof larger the experiment number in ofthe num- CW-spinning figuresber of figures in the interpreted leg-outstretched as spinning version CW in of any the of experiment the remaining (M combinations = 56.26%) ofthan hemifield in the arm-outstretchedof presentation version and of participant’s the experiment sex (all (Mp > = 0.08;40.03%; Supplementary t47 = 2.460; Materialp = 0.070) Table in the S9). RVF, and no difference was observed between the arm- and leg-outstretched version of 4. Discussion the experiment in the number of figures interpreted as spinning CW in any of the remaining combinationsIn the of present hemifield study, of we presentation investigated whether and participant’s the lateralized sex presentation (all p > 0.08; of rotating ambiguous human bodies affects their perceived handedness/footedness (in which case Supplementary Material Table S9). motor representations would be mainly involved) or their perceived spinning direction (in which case visual representations would be mainly involved), or even both. Results 4. Discussion indicated that the lateralized presentation of the stimuli affected both their perceived limb In the presentlaterality study, and we their investigated perceived spinning whether direction, the lateralized although thepresentation effect size wasof rotat- larger in the 2 2 ing ambiguouslatter human (ηp = bodies 0.06) than affects in the their former perceived (ηp = 0.12) handedness/footedness case. In line with our previous (in which studies with case motor representationsambiguous human would silhouettes be mainly [1–6 ],involved) with the exceptionor their perceived of one out ofspinning three experiments direction (in which case visual representations would be mainly involved), or even both. Results indicated that the lateralized presentation of the stimuli affected both their perceived limb laterality and their perceived spinning direction, although the effect size was larger in the latter (ηp2 = 0.06) than in the former (ηp2 = 0.12) case. In line with our previous studies with ambiguous human silhouettes [1–6], with the exception of one out of three experiments in [6], the participants’ laterality score did not correlate with the percentage of figures interpreted as right-limbed or spinning CW.

Symmetry 2021, 13, 1349 14 of 19

in [6], the participants’ laterality score did not correlate with the percentage of figures interpreted as right-limbed or spinning CW. As regards limb laterality, participants perceived a larger number of right-limbed rather than left-limbed figures. This effect corresponded to a statistical trend to interpret a larger number of figures as CW-spinning in the outward- rather than in the inward-rotation condition. These differences were significant in the RVF but not in the LVF, and a larger number of figures were interpreted as right-limbed in the RVF than in the LVF. These results are consistent with our previous studies showing that ambiguous human figures are interpreted more frequently as right- rather than left-limbed [1–3,5,6] and that a larger number of such stimuli is interpreted as right-limbed in the RVF than in the LVF [4], indicating that the left and right hemispheres can prompt a biased interpretation of ambiguous stimuli, inducing the perception of right- and left-limbed movements, respectively. Therefore, the present study corroborates the proposal of a hemispheric specialization in the embodiment of observed movements, in line with previous studies with lateralized presentation of stimuli showing an association between the hemispheric representation of the observer’s body and the visual representation of the observed bodies [21–23]. Moreover, male but not female participants perceived a larger number of right- rather than left-limbed figures (corresponding to the fact that only male participants interpreted a larger number of figures as CW-spinning in the outward- rather than in the inward-rotation condition), and the number of figures interpreted as right-limbed was larger for male than for female participants (corresponding to a statistical trend indicating that male participants, compared with female participants, interpreted a larger number of figures as CCW-spinning in the inward- rotation condition). This result might indicate that the bias for the right limb could be stronger in male rather than female individuals and seems to be consistent with the finding that the advantage of left-handers in sport is larger for male than for female players [47–49]. However, this conclusion must be considered with caution because the larger proportion of figures interpreted as right-limbed in male than in female participants was not predicted, and it was due mainly to the inward-rotation condition of the leg-outstretched version of the experiment (corresponding to the larger number of figures interpreted as spinning CCW by male than by female participants in the leg-outstretched version of the experiment) and more specifically to the inward-rotation condition of stimuli presented in the RVF in the leg-outstretched version of the experiment (corresponding to the larger number of figures presented in the RVF interpreted as spinning CCW by male than by female participants in the leg-outstretched version of the experiment). Thus, also because every significant effect 2 including sex showed only a small to medium-low effect size (with ηp ranging from 0.05 to 0.08) and because we observed inconsistent results in a previous study [6], this finding should be corroborated by further studies specifically aimed at testing the hypothesis that, body compared with females, males could exhibit a larger attentional and perceptual bias toward the right side of others. As regards spinning direction, participants perceived a larger number of CW- rather than CCW-spinning figures in the LVF, whereas no difference was observed in the RVF. This effect corresponded to the fact that participants interpreted a larger number of figures as right-limbed in the outward- rather than in the inward-rotation condition in the LVF, whereas no difference was observed in the RVF. Moreover, a larger number of figures were interpreted as spinning CW in the LVF than in the RVF (corresponding to the fact that participants interpreted a larger number of figures as right-limbed in the RVF rather than in the LVF in the inward-rotation condition, and a larger number of figures as right-limbed in the LVF rather than in the RVF in the outward-rotation condition). These results are consistent with those reported by Alipour and Kazemi [24], who found analogous effects by presenting the spinning dancer illusion in the two hemifields. With the exception of that study, no previous research examined the effects of eccentricity on the perception of the spinning direction of bistable stimuli. As suggested by Alipour and Kazemi, it is plausible that the characteristics of optic flow, which can be represented by the motion vectors on the visible surfaces of two rotating cylinders (one located in the LVF and rotating Symmetry 2021, 13, 1349 15 of 19

CW and the other located in the RVF and rotating CCW) may help to explain this trend. In line with this interpretation, the study by Burton et al. [27] indicated that the right and left hemispheres show a bias for the CW and CCW direction, respectively. Such an optic-flow account may be criticized because it implicitly assumes a forward movement (i.e., approach) rather than a backward movement (i.e., recession) on behalf of either the observer or the stimulus. Nonetheless, it is important to emphasize how movements receding from the fixation point are much rarer than those approaching to it (humans, like other animals, usually move toward the objects they are looking at, and—from an evolutionary standpoint—fast backward movements constitute an exception also for humans, who experience it mainly when traveling by car, train, or ship). Furthermore, also as regards the stimuli used in this experiment, it is interesting to note how ambiguous stimuli representing humans (regardless of whether they consist of dynamic point-light displays or static silhouettes) are perceived more often as approaching/from the front than receding/from the back [1–4,35,36]. In particular, Schouten et al. [35] have suggested that an individual who is moving toward the observer should be a more relevant stimulus compared with an individual who is moving away. Accordingly, the visual system would assess the potential cost of misinterpreting others’ actions and intentions, and assuming that someone is receding rather than approaching could be more costly compared with assuming that someone is approaching rather than receding (in particular, the facing bias would be congruent with the fact that approaching human walkers can convey a greater level of threat compared with receding human walkers). Therefore, also due to the absence of better alternative interpretations, the explanation based on the optic flow seems to be the most plausible (as well as in line with the different biological relevance of approaching compared with receding stimuli). As previously stated, the same hemifield-specific rotational bias could account for the tendency to perceive stimuli as moving away from the fixation point [21,42], a long since well-known perceptual preference that has often been linked to the common experience of optic flow during forward locomotion [50–55]. As already stated, the hemifield of presentation showed a larger effect size on the 2 perceived spinning direction (with a medium-high ηp for the relevant interaction) than 2 on the perceived limb laterality (with a medium ηp for the relevant interaction). These results corroborate our previous proposal that, differently from other tasks such as the imagination of others’ actions [56–59], the implicit representation of others’ handedness is affected more by visual than by motor processes during the perception of ambiguous human silhouettes [1–6]. Noteworthy, the same conclusion about a relatively greater role for motor and visual representations, respectively, during the imagination of others’ actions [56–59] and the perception of ambiguous human silhouettes [1–6] can be drawn by the fact that a positive correlation between participants’ right-handedness and the bias toward the right side of bodies is observed in the former but not in the latter task. The crucial role of perceptual processes is also corroborated by the finding that a specific training consisting in the visual presentation of right- and left-handedness can intensify or attenuate, respectively, the advantage in predicting the outcome of right- rather than left- handed actions [13]. Another factor possibly affecting the bias toward the right limb might be stress, which is known to modulate hemispheric asymmetries, as well as cognitive and sport performance [60–63]. On the other hand, non-invasive brain stimulation has gained increasing popularity as a method to improve cognitive and sport performance [64–68], and one could wonder whether combining brain stimulation and perceptual training might exert even stronger effects in reducing the attentional and perceptual bias toward the right limb observed in sport. The fact that the effect of the hemifield of presentation on the perceived spinning rotation overcame that on the perceived limb laterality could explain why in the present study 2 the effect size for the main factor “perceived limb laterality” was small (ηp = 0.04) and relatively smaller compared with that observed in our previous studies using similar stimuli 2 shown in central presentation, in which it ranged from medium (ηp = 0.10; unpublished 2 data from [5]) to large (ηp = 0.24; [6]). It should be also noticed that, differently from propos- Symmetry 2021, 13, 1349 16 of 19

als suggesting a role for embodiment in the hemifield-specific perceptual biases observed during the perception of human bodies or body parts [2,4,21–23], Williamson et al. [42] questioned the involvement of motor representations in biasing the perceived direction of point light-walkers in the two visual hemifields, pointing out that the bias to report perceiving right-facing walkers in the right visual field was not observed exclusively with stimuli representing human bodies. Aside from the differences in the experimental paradigm that necessarily limit the generalizability of such a conclusion, it should be considered with caution in light of our present findings, which show that when a possible confounding factor such as the perceptual bias for forward-facing motion is controlled for by using both inward- and outward-rotating stimuli, the hemifield of presentation biases both the perceived spinning direction and—although to a lesser extent—the perceived limb laterality of ambiguous human bodies. Noteworthy, converging evidence seems to indicate, regardless of the stimuli used, a similar pattern of results: in central vision, an attentional and perceptual bias toward the right limb is observed when participants are required to report the orientation (front/back) of static ambiguous human silhouettes [1,3], the spinning direction (CW/CCW) of dynamic ambiguous human silhouettes [3,5,6], and the facing direction (right/left) of masked point-light walkers [19,20]; in peripheral vision, as also observed in the present study, such a bias is abolished in the LVF and increased in the RVF [2,4,42]. A clearer picture of the role of visual and motor representations in lateral perceptual biases toward the human body could emerge from future studies investigating—in both central and peripheral vision—the correlations between the strength of such biases for static ambiguous human silhouettes, dynamic ambiguous human silhouettes, and masked point-light walkers. Further studies should also investigate the role of optic flow and related hemisphere-specific rotational biases in the relationship between motor and perceptual preferences (e.g., [43]; for reviews, see [69,70]). Finally, it is worth addressing some possible limitations of the present study. First, we asked participants to report the perceived spinning direction of the silhouette by indicating which of two colored arrows represented their percept. Whereas such a response modality undoubtedly unveils whether participants perceived a CW or CCW rotation, the association between the perceived spinning direction and the perceived handedness of the silhouette is obviously less straightforward, although reasonable. In order to legitimate our decision, we would like to point out that observers can report more easily the perceived spinning direction rather than the perceived laterality of ambiguous stimuli like those adopted here, and nonetheless—as also found in the present study—a population bias is observed as regards perceived limb laterality but not perceived spinning direction [3,5,6]. Therefore, it is plausible that—at least on an implicit level—the perceived spinning direction of the silhouette unveils its perceived limb laterality, an idea that would be strongly corroborated if a positive correlation were found between the perceptual bias for the right limb observed in studies with ambiguous human silhouettes [1–6] and the perceptual advantage for right-limbed movements observed in sport studies [7–13]. Second, we discarded trials in which participants moved their gaze from the fixation point through a visual inspection of the video recordings of their face, acquired during the experiment, rather than by using an eye-tracking device, which might reduce the precision of our exclusion procedure. This limit could be overcome by resorting to eye-tracking measures in future studies.

Supplementary Materials: The following are available online at https://www.mdpi.com/article/ 10.3390/sym13081349/s1, File S1: Supplementary Tables S1–S9. Table S1: Percentage of figures perceived as right-limbed by female and male participants according to outstretched limb and type of rotation; Table S2: Percentage of figures perceived as right-limbed in the arm- and leg-outstretched versions of the experiment according to participant’s sex and type of rotation; Table S3: Percentage of figures perceived as right-limbed in the inward- and outward-rotation conditions according to participant’s sex and type of rotation; Table S4: Percentage of figures perceived as right- and left-limbed according to participant’s sex, outstretched limb, hemifield of presentation and type of rotation; Table S5: Percentage of figures perceived as right-limbed in each hemifield according to participant’s sex, outstretched limb and type of rotation; Table S6: Percentage of figures perceived as right-limbed Symmetry 2021, 13, 1349 17 of 19

by female and male participants according to outstretched limb, hemifield of presentation and type of rotation; Table S7: Percentage of figures perceived as spinning clockwise (CW) and counterclockwise (CCV) according to participant’s sex and outstretched limb; Table S8: Percentage of figures perceived as spinning clockwise (CW) by female and male participants according to outstretched limb and hemifield of presentation; Table S9: Percentage of figures perceived as spinning clockwise (CW) in the arm- and leg-outstretched versions of the experiment according to participant’s sex and hemifield of presentation. Author Contributions: Conceptualization, C.L. and D.M.; methodology, C.L. and D.M.; formal analysis, C.L., D.M., C.P., S.T. and G.M.; investigation, C.L., C.P., S.T., L.P.Z. and I.A.; resources, L.T.; writing—original draft preparation, C.L. and D.M.; writing—review and editing, C.P., S.T., L.P.Z., G.M., I.A. and L.T.; visualization, C.L. and G.M.; supervision, D.M. and L.T.; project administration, D.M. All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding. Institutional Review Board Statement: The study was conducted according to the guidelines of the Declaration of Helsinki, and approved by the Institutional Review Board of Psychology of the Department of Psychological Sciences, Health, and Territory of the University of Chieti (protocol code 21003). Informed Consent Statement: Informed consent was obtained from all subjects involved in the study. Data Availability Statement: The data that support the findings of this study are available from the corresponding authors upon request. Conflicts of Interest: The authors declare no conflict of interest.

References 1. Marzoli, D.; Lucafò, C.; Pagliara, A.; Cappuccio, R.; Brancucci, A.; Tommasi, L. Both Right- and Left-Handers Show a Bias to Attend Others’ Right Arm. Exp. Brain Res. 2015, 233, 415–424. [CrossRef] 2. Marzoli, D.; Pagliara, A.; Prete, G.; Malatesta, G.; Lucafò, C.; Padulo, C.; Brancucci, A.; Tommasi, L. Lateralized Embodiment of Ambiguous Human Silhouettes: Data on Sex Differences. Data Brief 2019, 25, 104009. [CrossRef][PubMed] 3. Marzoli, D.; Lucafò, C.; Padulo, C.; Prete, G.; Giacinto, L.; Tommasi, L. Inversion Reveals Perceptual Asymmetries in the Configural Processing of Human Body. Front. Behav. Neurosci. 2017, 11, 126. [CrossRef][PubMed] 4. Marzoli, D.; Pagliara, A.; Prete, G.; Malatesta, G.; Lucafò, C.; Padulo, C.; Brancucci, A.; Tommasi, L. Hemispheric Asymmetries in the Processing of Body Sides: A Study with Ambiguous Human Silhouettes. Neurosci. Lett. 2017, 656, 114–119. [CrossRef] 5. Lucafò, C.; Marzoli, D.; Prete, G.; Tommasi, L. Laterality Effects in the Spinning Dancer Illusion: The Viewing-from-above Bias Is Only Part of the Story. Br. J. Psychol. Lond. Engl. 2016, 107, 698–709. [CrossRef][PubMed] 6. Lucafò, C.; Marzoli, D.; Zdybek, P.; Malatesta, G.; Smerilli, F.; Ferrara, C.; Tommasi, L. The Bias toward the Right Side of Others Is Stronger for Hands than for Feet. Symmetry 2021, 13, 146. [CrossRef] 7. Hagemann, N. The Advantage of Being Left-Handed in Interactive Sports. Atten. Percept. Psychophys. 2009, 71, 1641–1648. [CrossRef] 8. Loffing, F.; Hagemann, N.; Schorer, J.; Baker, J. Skilled Players’ and Novices’ Difficulty Anticipating Left- vs. Right-Handed Opponents’ Action Intentions Varies across Different Points in Time. Hum. Mov. Sci. 2015, 40, 410–421. [CrossRef] 9. Loffing, F.; Schorer, J.; Hagemann, N.; Baker, J. On the Advantage of Being Left-Handed in Volleyball: Further Evidence of the Specificity of Skilled Visual Perception. Atten. Percept. Psychophys. 2012, 74, 446–453. [CrossRef] 10. Loffing, F.; Hagemann, N. Zum Einfluss Des Anlaufwinkels Und Der Füßigkeit Des Schützen Auf Die Antizipation von Elfmeterschüssen. Z. Sportpsychol. 2015.[CrossRef] 11. Loffing, F.; Hagemann, N. Motor Competence Is Not Enough: Handedness Does Not Facilitate Visual Anticipation of Same- Handed Action Outcome. Cortex 2020, 130, 94–99. [CrossRef][PubMed] 12. McMorris, T.; Colenso, S. Anticipation of Professional Soccer Goalkeepers When Facing Right-and Left-Footed Penalty Kicks. Percept. Mot. Skills 1996, 82, 931–934. [CrossRef] 13. Schorer, J.; Loffing, F.; Hagemann, N.; Baker, J. Human Handedness in Interactive Situations: Negative Perceptual Frequency Effects Can Be Reversed! J. Sports Sci. 2012, 30, 507–513. [CrossRef] 14. Knoblich, G.; Flach, R. Action Identity: Evidence from Self-Recognition, Prediction, and Coordination. Conscious. Cogn. 2003, 12, 620–632. [CrossRef] 15. Faurie, C.; Raymond, M. Handedness, Homicide and Negative Frequency-Dependent Selection. Proc. Biol. Sci. 2005, 272, 25–28. [CrossRef] 16. Jacobs, A.; Pinto, J.; Shiffrar, M. Experience, Context, and the Visual Perception of Human Movement. J. Exp. Psychol. Hum. Percept. Perform. 2004, 30, 822–835. [CrossRef][PubMed] Symmetry 2021, 13, 1349 18 of 19

17. Marzoli, D.; Prete, G.; Tommasi, L. Perceptual Asymmetries and Handedness: A Neglected Link? Front. Psychol. 2014, 5, 163. [CrossRef] 18. Johansson, G. Visual Perception of Biological Motion and a Model for Its Analysis. Percept. Psychophys. 1973, 14, 201–211. [CrossRef] 19. Thornton, I.M.; Vuong, Q.C.; Bülthoff, H.H. A Chimeric Point-Light Walker. Perception 2003, 32, 377–383. [CrossRef][PubMed] 20. Williamson, K.E.; Jakobson, L.S.; Troje, N.F. A Right-Facing Bias in the Processing of Biological Motion? J. Vis. 2008, 8, 913. [CrossRef] 21. de Lussanet, M.H.E.; Fadiga, L.; Michels, L.; Seitz, R.J.; Kleiser, R.; Lappe, M. Interaction of Visual Hemifield and Body View in Biological Motion Perception. Eur. J. Neurosci. 2008, 27, 514–522. [CrossRef][PubMed] 22. Aziz-Zadeh, L.; Iacoboni, M.; Zaidel, E. Hemispheric Sensitivity to Body Stimuli in Simple Reaction Time. Exp. Brain Res. 2006, 170, 116–121. [CrossRef] 23. Parsons, L.M.; Gabrieli, J.D.; Phelps, E.A.; Gazzaniga, M.S. Cerebrally Lateralized Mental Representations of Hand Shape and Movement. J. Neurosci. Off. J. Soc. Neurosci. 1998, 18, 6539–6548. [CrossRef] 24. Alipour, A.; Kazemi, S. Dominant Right Hemisphere Controls Biased Rotation Perception. Psychol. Neurosci. 2015, 8, 435. [CrossRef] 25. Burton, A.; Radford, J. Thinking in Perspective: Critical Essays in the Study of Thought Processes; Routledge: Abingdon, UK, 1978; Volume 646. 26. Horn, B.; Klaus, B.; Horn, P. Robot Vision; MIT Press: Cambridge, MA, USA, 1986. 27. Burton, L.A.; Wagner, N.; Lim, C.; Levy, J. Visual Field Differences for Clockwise and Counterclockwise Mental Rotation. Brain Cogn. 1992, 18, 192–207. [CrossRef] 28. McBeath, M.K.; Morikawa, K. Forward-Facing Motion Biases for Rigid and Nonrigid Biologically Likely Transformations. Percept. Mot. Skills 1997, 85, 1187–1193. [CrossRef] 29. McBeath, M.K.; Morikawa, K.; Kaiser, M.K. Perceptual Bias for Forward-Facing Motion. Psychol. Sci. 1992, 3, 362–367. [CrossRef] 30. Hsu, P.; Taylor, J.E.T.; Pratt, J. Frogs Jump Forward: Semantic Knowledge Influences the Perception of Element Motion in the Ternus Display. Perception 2015, 44, 779–789. [CrossRef] 31. Bernstein, L.J.; Cooper, L.A. Direction of Motion Influences Perceptual Identification of Ambiguous Figures. J. Exp. Psychol. Hum. Percept. Perform. 1997, 23, 721–737. [CrossRef] 32. Pavlova, M.; Krägeloh-Mann, I.; Birbaumer, N.; Sokolov, A. Biological Motion Shown Backwards: The Apparent-Facing Effect. Perception 2002, 31, 435–443. [CrossRef] 33. Wotton, J.M.; Ferragamo, A.C. Ambiguous Animals: Mutable Mammal Biases Bird. Perception 2012, 41, 501–503. [CrossRef] 34. Bucher, N.M.; Palmer, S.E. Effects of Motion on Perceived Pointing of Ambiguous Triangles. Percept. Psychophys. 1985, 38, 227–236. [CrossRef] 35. Schouten, B.; Troje, N.F.; Brooks, A.; van der Zwan, R.; Verfaillie, K. The Facing Bias in Biological Motion Perception: Effects of Stimulus Gender and Observer Sex. Atten. Percept. Psychophys. 2010, 72, 1256–1260. [CrossRef] 36. Vanrie, J.; Dekeyser, M.; Verfaillie, K. Bistability and Biasing Effects in the Perception of Ambiguous Point-Light Walkers. Perception 2004, 33, 547–560. [CrossRef] 37. Doi, H.; Shinohara, K. Bodily Movement of Approach Is Detected Faster than That of Receding. Psychon. Bull. Rev. 2012, 19, 858–863. [CrossRef] 38. Franconeri, S.L.; Simons, D.J. Moving and Looming Stimuli Capture Attention. Percept. Psychophys. 2003, 65, 999–1010. [CrossRef] 39. Lewis, C.F.; McBeath, M.K. Bias to Experience Approaching Motion in a Three-Dimensional Virtual Environment. Perception 2004, 33, 259–276. [CrossRef] 40. Parker, A.; Alais, D. A Bias for Looming Stimuli to Predominate in Binocular Rivalry. Vision Res. 2007, 47, 2661–2674. [CrossRef] [PubMed] 41. Skarratt, P.A.; Cole, G.G.; Gellatly, A.R.H. Prioritization of Looming and Receding Objects: Equal Slopes, Different Intercepts. Atten. Percept. Psychophys. 2009, 71, 964–970. [CrossRef][PubMed] 42. Williamson, K.; Jakobson, L.; Troje, N. Life Detection in Central and Peripheral Vision. J. Vis. 2007, 7, 484. [CrossRef] 43. Malatesta, G.; Marzoli, D.; Tommasi, L. Keep a Left Profile, Baby! The Left-Cradling Bias Is Associated with a Preference for Left-Facing Profiles of Human Babies. Symmetry 2020, 12, 911. [CrossRef] 44. Simmons, J.P.; Nelson, L.D.; Simonsohn, U. A 21 Word Solution; Social Science Research Network: Rochester, NY, USA, 2012. 45. Liu, C.-H.; Tzeng, O.J.L.; Hung, D.L.; Tseng, P.; Juan, C.-H. Investigation of Bistable Perception with the “Silhouette Spinner”: Sit Still, Spin the Dancer with Your Will. Vis. Res. 2012, 60, 34–39. [CrossRef][PubMed] 46. Salmaso, D.; Longoni, A.M. Problems in the Assessment of Hand Preference. Cortex J. Devoted Study Nerv. Syst. Behav. 1985, 21, 533–549. [CrossRef] 47. Breznik, K. On the Gender Effects of Handedness in Professional Tennis. J. Sports Sci. Med. 2013, 12, 346–353. [PubMed] 48. Loffing, F.; Hagemann, N.; Strauss, B. Left-Handedness in Professional and Amateur Tennis. PLoS ONE 2012, 7, e49325. [CrossRef] 49. Raymond, M.; Pontier, D.; Dufour, A.B.; Møller, A.P. Frequency-Dependent Maintenance of Left Handedness in Humans. Proc. Biol. Sci. 1996, 263, 1627–1633. [CrossRef][PubMed] 50. Annett, M. Individual Variation in Directional Bias in Visual Perception. Perception 1983, 12, 71–84. [CrossRef] 51. Ball, K.; Sekuler, R. Human Vision Favors Centrifugal Motion. Perception 1980, 9, 317–325. [CrossRef] Symmetry 2021, 13, 1349 19 of 19

52. Dumoulin, S.O.; Baker, C.L.; Hess, R.F. Centrifugal Bias for Second-Order but Not First-Order Motion. JOSA A 2001, 18, 2179–2189. [CrossRef] 53. Fahle, M.; Wehrhahn, C. Motion Perception in the Peripheral Visual Field. Graefes Arch. Clin. Exp. Ophthalmol. 1991, 229, 430–436. [CrossRef][PubMed] 54. Georgeson, M.A.; Harris, M.G. Apparent Foveofugal Drift of Counterphase Gratings. Perception 1978, 7, 527–536. [CrossRef] [PubMed] 55. Lappe, M.; Rauschecker, J.P. Motion Anisotropies and Heading Detection. Biol. Cybern. 1995, 72, 261–277. [CrossRef][PubMed] 56. Marzoli, D.; Menditto, S.; Lucafò, C.; Tommasi, L. Imagining Others’ Handedness: Visual and Motor Processes in the Attribution of the Dominant Hand to an Imagined Agent. Exp. Brain Res. 2013, 229, 37–46. [CrossRef][PubMed] 57. Marzoli, D.; Lucafò, C.; Rescigno, C.; Mussini, E.; Padulo, C.; Prete, G.; D’Anselmo, A.; Malatesta, G.; Tommasi, L. Sex-Specific Effects of Posture on the Attribution of Handedness to an Imagined Agent. Exp. Brain Res. 2017, 235, 1163–1171. [CrossRef] 58. Marzoli, D.; Mitaritonna, A.; Moretto, F.; Carluccio, P.; Tommasi, L. The Handedness of Imagined Bodies in Action and the Role of Perspective Taking. Brain Cogn. 2011, 75, 51–59. [CrossRef] 59. Marzoli, D.; Palumbo, R.; Di Domenico, A.; Penolazzi, B.; Garganese, P.; Tommasi, L. The Relation between Self-Reported Empathy and Motor Identification with Imagined Agents. PLoS ONE 2011, 6, e14595. [CrossRef] 60. Berretz, G.; Packheiser, J.; Wolf, O.T.; Ocklenburg, S. Dichotic Listening Performance and Interhemispheric Integration after Stress Exposure. Sci. Rep. 2020, 10, 20804. [CrossRef] 61. Schultheiss, O.C.; Riebel, K.; Jones, N.M. Activity Inhibition: A Predictor of Lateralized Brain Function during Stress? Neuropsy- chology 2009, 23, 392–404. [CrossRef] 62. Hardy, L. Psychological Stress, Performance, and Injury in Sport. Br. Med. Bull. 1992, 48, 615–629. [CrossRef] 63. Palmer, L. The Relationship Between Stress, Fatigue, and Cognitive Functioning. Coll. Stud. J. 2013, 47, 312–325. 64. Penolazzi, B.; Di Domenico, A.; Marzoli, D.; Mammarella, N.; Fairfield, B.; Franciotti, R.; Brancucci, A.; Tommasi, L. Effects of Transcranial Direct Current Stimulation on Episodic Memory Related to Emotional Visual Stimuli. PLoS ONE 2010, 5.[CrossRef] 65. Friehs, M.A.; Dechant, M.; Vedress, S.; Frings, C.; Mandryk, R.L. Shocking Advantage! Improving Digital Game Performance Using Non-Invasive Brain Stimulation. Int. J. Hum.-Comput. Stud. 2021, 148, 102582. [CrossRef] 66. Martin, D.M.; Liu, R.; Alonzo, A.; Green, M.; Loo, C.K. Use of Transcranial Direct Current Stimulation (TDCS) to Enhance Cognitive Training: Effect of Timing of Stimulation. Exp. Brain Res. 2014, 232, 3345–3351. [CrossRef][PubMed] 67. Ruf, S.P.; Fallgatter, A.J.; Plewnia, C. Augmentation of Working Memory Training by Transcranial Direct Current Stimulation (TDCS). Sci. Rep. 2017, 7, 876. [CrossRef][PubMed] 68. Friehs, M.A.; Güldenpenning, I.; Frings, C.; Weigelt, M. Electrify Your Game! Anodal TDCS Increases the Resistance to Head Fakes in Basketball. J. Cogn. Enhanc. 2020, 4, 62–70. [CrossRef] 69. Karim, A.K.M.R.; Proulx, M.J.; Likova, L.T. Anticlockwise or Clockwise? A Dynamic Perception-Action-Laterality Model for Directionality Bias in Visuospatial Functioning. Neurosci. Biobehav. Rev. 2016, 68, 669–693. [CrossRef] 70. Rogers, L.J. Asymmetry of Motor Behavior and Sensory Perception: Which Comes First? Symmetry 2020, 12, 690. [CrossRef]